Ford 390 Block Surgery

Turning a mild 390 Ford engine in to something wild

Ken Sheffer

December 3, 2004

In the last installment of this continuing saga, we ended our dynosession at Roush Racing when the crank decided it'd had enough, just aswe were getting warmed up. The crank destroyed the rod bearing, whichmelted to the rod and crank. The end result was two ruined rods. Onethrew its cap through the side of the block and subsequently broke inhalf.

After a thorough inspection of the block, we found the following:

1. Block skirt "windowed;"

2. Small crack and pair of brinelled spots in opposite side of blockskirt;

3. Two cylinders damaged at the bottom--one with crack and dimple inwall;

All of the important parts of the block were intact and without damage.We decided to repair the mentioned trouble spots and build anotherengine. Let's look at what it took for the guys in Jack Roush's RaceEngine Shop to save our damaged block.

Two of the processes we've had to go through can induce some degree ofdistortion to the cast-iron structure. By far, the greatest degree ofstress would come from the welding. In order to successfully weld iron,it's necessary to preheat the work piece. Then, when the whole block (inthis case) was heated, the actual welding could progress.

Chris Razor of Hi-Tech Welding Inc. was chosen to do the work. His reputation includes some very sensitive work for Ford in past projects.It's also really handy that his shop is less than a mile from the Roush facility. After a discussion with Chris, I went back to my shop and took a "whizzer wheel" to one of the block pieces left from the research into improving the oil passages in the ordinary FE block. I cut out a sufficiency of the block skirt and took it back to Chris.

Further discussion centered on the advisability of using the Meta-Lax stress-relieving process as an adjunct to producing the finest possible repair. After listening to Chris, we reached this conclusion in this manner.

In the metro Detroit area, there are a number of steel-manufacturing concerns. The giant crucibles that hold the molten metal during the steel-making process require repair on a regular basis. It's not unusual to have to cut a 6x6-foot section out of one and weld in a patch. The wall of the crucible is 5 inches thick. Such a repair was generally good for as much as two or three months. The repair would then fail and have to be redone. The addition of the Meta-Lax process to the rebuilding effort was so successful that repairs would last as much as three years.

It's beyond the scope of this article to explore the metallurgic reasons for this improvement. In simple fashion, the improvement in grain structure, not only the weld, but also the entirety of parent metal,brings about the amelioration. I had to have it. Luckily, Chris has the necessary equipment.

Another benefit was discovered at Hi-Tech. The grinding and welding made it clear that this block has a high nickel content. Almost all blocks from Ford during the early '60s were ordinary gray iron. My sources all agree it would be unusual to have the nickel. The grinding sparks and welding ease made it clear that, at least in this case, nickel is present.

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With the Meta-Lax equipment standing by, we placed the block on Chris' welding table. The legs of this structure are isolated from the floor by special rubber pads. Next, the vibratory inducer was clamped in place on the back edge of the work surface. A transducer to send information tothe control panel was attached in its turn.

When the equipment is turned on, the only sign that it's working is a faint hum, and it's noticeable that tools on the work surface tend to"walk around." The resonance of the block was ascertained from the meter readings on the control panel and the proper settings made. Once that's done, the machine does its work without assistance for about 10-15minutes. Further meter readings tell you preparation is complete. It's time to take the "rosebud" torch and begin the heating of the welding site. A resetting of the Meta-Lax machine for welding processes is necessary.

Chris has a never-ending search for improvements in welding--both in technique and materials. He's engaged in an exploration to find a better rod alloy for cast-iron welding. His partner in this exploration is one of the major rod manufacturers. The search is open-ended, and he'll havean even better answer two months from now than he does at present.

The actual welding of the patch was almost anticlimactic. He'd ground out the broken hole to a rounded-rectangular shape and traced the hole onto the piece of patch material from the other block. The shape was band-sawed and then ground until it could be urged into the hole. When hammer taps put it into position, he picked up his TIG-torch and started to weld.

After tacking it into place in several areas, he welded about a 3/8-inchspot. Next, he took a chipping hammer, modified with a rounded end instead of a point, and peened the bead he'd just formed. He jumped across to the other side of the patch and repeated the process.Crisscrossing in this fashion, he had the patch all in place withinabout 10 minutes. He repeated the entire process on the outside of thepatch. When the welding was complete, he reset the Meta-Lax andre-treated the entire work piece. When it had cooled, it was ready forthe truck to take it back to the Race Shop.

The next task was to replace the cylinder surfaces damaged when theengine came apart. When the rod broke, the piston slammed the head,instantaneously jamming up the combustion chamber surface and crackingthe water jacket into one head-bolt hole and across into one of thepipe-plugged upper openings. (I'm going to try to repair this head foranother project; our new engine will be a different configuration.) Thebig end of the rod flailed around and, in its movements, damaged thebottoms of the two closest cylinders and the bottom of one lifter silo.These holes would require sleeves.

We started by taking extensive sonic readings up and down the cylinderwalls. A trip to the catalog told us the sleeve size that would give themost strength, taking into account the necessity of having support fromthe original block. We ultimately arrived at a compromise of these twodimensions and ordered the sleeves.

Having bored the block to the correct size, the sleeves were installedin a lathe and cut to a length that would leave material standing"proud" of the deck surface after installation. These cuts also madesure the ends of the sleeves were square to the walls.

The Roush Race Shop procedure for installing a sleeve is based on theuse of liquid nitrogen as a cooling (and therefore shrinking) agent.With the block still locked into the boring machine for stability, aspecially constructed stainless steel "cooler" is filled with liquidnitrogen. The sleeves are placed in this material and left for 10minutes or more. With everything set ready, the sleeve is plucked fromthe clear liquid in the "cooler" using a pair of pliers. Now shrunken bythe cold, it is slipped into the bored block. At ambient temperature,the sleeve is an interference fit into the block. Super-cooled in thisfashion, it shrunk and will slide into place. However, it's necessary tobe prepared. On first exposure to the air, the humidity immediatelycauses a thick coat of frost to form. The first sleeve had to be nudgedinto place with a tool made for this purpose. A honing plate isimmediately torqued into place over the deck end of the sleeve withsteel straps, making sure pressure is holding the sleeve down againstthe step left at the bottom of the bored cylinder.

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The same activity was carried out with the other sleeve. The immediatelyadjacent air was so dried by the first sleeve frosting over that therewas significantly less frost in evidence on the second procedure. Thesecond sleeve simply slid into place and was forced down with anotherhoning plate. We let it sit several hours until the whole thing hadreturned to room temperature. A touch-cut is taken across the decks toremove the exposed sleeve edge, and the block is ready for honing andthe other operations necessary to return it to service.

Change of Plans

The original intention for our "mild" 390 was to use it as the powerplant for my '63 F-100 ICB pickup. That's not going to work now.Our plans for the "wild" 390, at present, go like this:

1. In order to make all cylinders exactly the same, the finished boresize is projected to be 4.090.

2. The crank will be one of the new SCAT strokers with a 4.25 dimension.

3. Jim Dove and I are collaborating on a special set of hisDOVE-6049-PIE head castings. These are of modernized High Riser design,with valves and valve locations optimized for the above bore size.

4. The manifold will be modified to take fuel-injection hardware.

5. This engine will be used, in a car not available at present, for amulti-year {{{Bonneville}}} attack.

The engine will have all the most up-to-date hardware and accoutrements.A little quick math will show that displacement should be about 446 ci.It started life as a 390. The heads have been shown to flow more than400 cfm on the intake and 300 on the exhaust. We'll have all the solidroller cam the flow can use. What do you think the dyno will say?